Boxerworks.com

Anybody ever try and stroke an airhead? And what happened to the forum?? I used to be all over this thing and i had to re-register...

awaffa22003 wrote:Anybody ever try and stroke an airhead? And what happened to the forum?? I used to be all over this thing and i had to re-register...

I read about a guy in Great Britain that was building big stoke cranks. I can't remember if he was marketing them or just experimenting. I'm surprised more hasn't been done in that respect. Sorry, I can't find a link.

There are plenty of crank grinders that can weld up, straighten and regrind an airhead crank to a longer stroke. How much would be a matter of figuring out how long of a stroke could be accomodated inside the crankcase....maybe with some clearance grinding here and there. There are short pistons already available for standard length cylinders and a longer stroke. Of course plates can be installed under the cylinders to accomodate longer strokes also.

awaffa22003 wrote:Anybody ever try and stroke an airhead? And what happened to the forum?? I used to be all over this thing and i had to re-register...

More than fifteen years ago, I was corresponding with a guy from Germany who had a BMW Motorsport connection. He had access to all sorts of factory hot rod parts...including stroked crankshafts. Based on my inability to even consider paying for some of the "lesser" parts, I never did ask about pricing on the crankshafts.

I have, on occasion, been known to stoke my old bike on especially cold mornings in hopes of getting a successful start. Usually just a bit of caressing along the tanks side is sufficient.

moonbeamerll wrote:I have, on occasion, been known to stoke my old bike on especially cold mornings in hopes of getting a successful start. Usually just a bit of caressing along the tanks side is sufficient.

I remember draining the oil to heat it on the stove in a pan and put it back into the motor to get the bike to start on really cold mornings, but then we were riding in the snow!

twist wrote:

moonbeamerll wrote:I have, on occasion, been known to stoke my old bike on especially cold mornings in hopes of getting a successful start. Usually just a bit of caressing along the tanks side is sufficient.

I remember draining the oil to heat it on the stove in a pan and put it back into the motor to get the bike to start on really cold mornings, but then we were riding in the snow!

My new CCC* starter sure helps the cold weather starting. It's been a bit below freezing the last few days and it spins over like crazy.


*CheepCheezeChineeze

just curious, stroking a motor involves longer con rods, no? I read in here something about grinding the crank to stroke the engine. Why can't stroking the engine be achieved with con rods, pistons and modifications to cylinders and heads?

twist wrote:just curious, stroking a motor involves longer con rods, no? I read in here something about grinding the crank to stroke the engine. Why can't stroking the engine be achieved with con rods, pistons and modifications to cylinders and heads?

No, stroking does not involve longer con rods. Longer rods equally move the top of the stroke and the bottom of the stroke further away from the center of the crank, but the top and bottom remain the same distance apart. It does not change how far the pistons travel. Only moving the rod journal further away from the centerline can do that. The stroke is only defined by the crankshaft. In fact, the only thing defined by the crankshaft is: the stroke, the crank timing, and how far apart the cylinder's centerlines are. Even the crank timing is not defined only by the crank (a 180 degree crank does not have 180 degree timing in a V engine).

If you have seen the discussions here about putting longer rods into a Boxer, they are about something different. Longer rods change the angle of the rods vs. the crank, and thus change the leverage the rods have on the crank. This change in the geometry also changes the speed of the piston near the top and bottom of the stoke. This can change the torque production of the motor.